FEB., 1912. MamMAts oF ILLINOIS AND WISCONSIN—CoRY. 209 
of the hairs on the under parts are dark plumbeous and the tips 
white or buffy white, the dark parts being nearly or quite concealed, 
but occasionally the under. fur shows through, giving a gray tinge 
to the under parts; adults often have a patch of pale, sometimes 
whitish, fur surrounding the gland on the flank. 
Dark phase: Occasionally specimens representing a dichromatic 
or dark phase of pelage are taken; the reddish brown back is replaced 
by dusky and the general coloration is darker and grayer. In the 
large number of specimens examined I have seen only. one in this 
pelage from Wisconsin. 
Measurements — (12 adult specimens from northern Wisconsin.) 
Total length, 5.10 to 6 in. (130 to 154 mm.); tail vertebre, about 
1.37 in. (30 to 41 mm.); hind foot, about .73 in. (18 to 20 mm.). 
Remarks — The Museum series contains 25 apparently not fully adult 
specimens which are small, several having a total length of 118 to 
125 mm., and are very similar in size and coloration to specimens 
of E. g. loringi from Dakota. Other specimens from the same 
locality, however, are of normal size. There is considerable varia- 
tion in size of the adults of this species, as will be seen by the follow- 
ing measurements of 12 selected specimens from different localities 
in northern Wisconsin. 
Total Length. Tail Vertebre. Hind Foot. 
Spread Eagle, Florence Co... ou 147 mm. 41 mm. 19 mm. 
Spread Eagle, Florence Co.... o& 144 “ 39 19 “ 
Conover, Vilas Co........... roa Teo 48°" 19 “ 
Conover, Vilas Co........... of 130 “ ao, 185 “ 
Conover, Vilas Co........... Q 139 “ ao * 18.5 " 
Lac Vieux Desert, Vilas Co... o& 154" 38 20 
Lac Vieux Desert, VilasCo... of 135 “ 32 “ im * 
Lac Vieux Desert, Vilas Co... 9 sz 39 io 
Lac Vieux Desert, Vilas Co... 9 142 “ 34 1 
Lac Vieux Desert, Vilas Co. . Q 134 30 i 
Upper St. Croix Lake, Bowe: 
Las CO} cscs ave eee eee of A 32 “ 18 
Upper St. Croix Lake, Doug- 
TAS COnatalit taal eden ea Q 149 “ 38 185 “ 
The Red-backed Mouse is a woodland species, frequenting low 
ground in heavy timber, sphagnum bogs and banks of streams, although 
like many other species of similar habitat, it occasionally resorts to 
fields and pastures bordering the woods. 
It is more diurnal in its 
habits than others of our Mice and is not uncommonly to be seen run- 
ning about in the day time. 
It is found in favorable localities throughout the greater part of 
Wisconsin except, perhaps, in some of the extreme southern and south- 
